Adhesion
by AnotherSpoonyBard
Summary: Adhesion is the tendency of dissimilar things to cling to one another. Such coexistence is most often temporary, particularly when other, stronger forces act against it. Or: in which Rukia learns the truth about Hisana—and Byakuya.
1. Chapter One: Choice and Conscience

_Disclaimer:_ I do not own Bleach.

* * *

I almost called this fic _Kuchiki Family Values_. Too bad I have a thematic titling thing for this AU.

Speaking of which, if you got here some other way than via the first two parts of the _Chaos Theory_ universe... be aware that this story takes place in an increasingly-divergent AU from canon. The big things to know are that Ichigo died as a kid and Karin, Yuzu, and Uryū(!) are (or will be, at the point this takes place) shinigami. Nearly everything in this particular fic should make sense as long as you have those extra facts in mind.

* * *

 _Adhesion_

A Bleach Fanfic

Chapter One: Choice and Conscience

* * *

We cannot live, except thus mutually  
We alternate, aware or unaware,  
The reflex act of life: and when we bear  
Our virtue onward most impulsively,  
Most full of invocation, and to be  
Most instantly compellant, certes, there  
We live most life, whoever breathes most air  
And counts his dying years by sun and sea.  
But when a soul, by choice and conscience, doth  
Throw out her full force on another soul,  
The conscience and the concentration both make  
mere life, Love. For Life in perfect whole  
And aim consummated, is Love in sooth,  
As nature's magnet-heat rounds pole with pole.

 _Love_ \- Elizabeth Barrett Browning

* * *

The teacup was still slightly too hot. But she'd only just picked it up, and she'd feel foolish setting it down too soon. Rukia discreetly adjusted her grip, not letting her fingers remain too long or too heavily on any one spot, in hopes of being able to bear out the cooling process with some modicum of dignity.

Across from her, Byakuya was as silent and still as ever. She thought that perhaps this was meant to be interpreted as serenity on his part, but recent insights into stoic personalities had gleaned her the knowledge that a lack of outward disruption was not to be equated with actual calm.

Beyond this singular observation, she could read him no further than she had before. She knew he didn't _dislike_ her—or, at least, he felt obligated to look after her. This, he had told her outright. A promise to her sister. They also had tea like this now, once a week, on Tuesdays because those were light on divisional training for both of them. Could it be counted as a tradition after a year? She thought so—a tradition of sitting in the same room, drinking tea, and not really talking much. He did occasionally ask her about things at the Thirteenth. She asked him about the Sixth to be polite; honestly Renji's answers were more informative and much more comfortable to seek.

Her fingers were burning. She gave up and set down the cup without having taken a sip.

"How are your lessons?"

Rukia, startled by the sound of his voice, looked up too sharply. "Fine, nii-sama."

They were awful.

She didn't think she was cut out for this noblewoman business. In some ways, life had been much easier when Byakuya had completely ignored her existence. Adapting to the military culture of the Gotei 13 was much easier than trying to learn how to comport herself around people of _distinction_ , never mind the considerable overlap.

"And your instructor?"

Possibly scarier than Zaraki-taichō, and twice as mean.

"Fujita-san is well-versed in her subject areas, and a very meticulous instructor."

Renji had used the words 'old bat.' Rukia thought that characterization had the benefit of being true.

"I see your diplomatic instinct has been sharpened to a fine point." Byakuya's tone didn't change—it was flat, emotionless, and dry. But… was he implying…?

His expression also remained the same, but he met her eyes over the rim of the teacup he held, taking a careful sip. Rukia wasn't sure how she was meant to reply to that.

"Sorry," she murmured. She supposed he must be subtly chiding her for her disingenuousness. It probably wasn't that hard to tell, for someone as practiced at this kind of thing as him.

He didn't reply. Rukia shifted uncomfortably in her seiza. She wished she were somewhere else. Her eyes found the window to the outside, but she forced them back to the table in front of her.

"I guess Hisana was probably better at all this comportment stuff than I am." Rukia still wasn't sure what to make of that, sometimes. Her sister had been Lady Kuchiki, for however brief a time. Rukia wasn't lady of anything—not really.

Byakuya's teacup made a soft clink as he placed it back on the table. Everything he did was elegant. "On the contrary. She was far worse."

Rukia felt her eyes widen fractionally. Lifting her head, she blinked at him. "She was? But…"

Byakuya didn't confirm it again. He'd already made the statement; she supposed he saw no need to repeat himself. She had, after all, clearly heard him. But in all the time since they'd started… talking to each other, if that's what this was, he'd never again mentioned Hisana. A door had cracked open here.

Rukia stepped through it.

"How did the two of you meet, anyway? If she was from Inuzuri…" She could not picture her brother ever going there. For any reason. Not even shinigami patrols made it that far out into the Rukongai.

He regarded her steadily. She still had no idea what in the world he could be thinking. For a moment, Rukia feared she might have asked something she should not have—perhaps he wouldn't want to talk about it. No one here talked about Hisana much; no one anywhere did. Was that because Byakuya had some kind of moratorium on the topic?

"Would you like to hear the story? It is… somewhat long, in total."

He was offering?

"I don't have any other pressing matters today, nii-sama. And… yes. I would like to know. About her."

And him, though she didn't say that.

He seemed to consider that for a moment, then inclined his head fractionally. "Very well."

* * *

Byakuya was dizzy.

He suspected this had something to do with the sake Kyōraku-taichō had been foisting on him all evening. While perhaps under ordinary circumstances he would have refused it after a certain point, Kyōraku was one of the few people at this gathering who could truly claim to be his peer. His superior, in fact—if only by seniority. He could not risk offense, considering.

He was not certain whose idea the celebration had been, only that it was ostensibly for his sake. But if that was so, it seemed rather unbecoming to leave him with the expenses, as he now found himself.

"I'm sorry to leave you, Byakuya-kun. But I really should get him home. He lost his latest vice-captain the other day, so I'm not sure anyone will remember to come looking for him." Ukitake supported a very intoxicated Kyōraku over his shoulders. He looked considerably wan himself, though not from liquor.

Byakuya could only nod his understanding, and try not to give sign of the considerable nausea the motion caused him.

Ukitake took his leave, and Byakuya found himself at an empty table. It had been much more occupied earlier, but most of the other celebrants had left at a reasonable hour. Much as he would have preferred to do. He considered the near-dozen empty sake cups and bottles around him with a slight frown.

Making to stand, he immediately fell back into his seat, certainly without making the choice to do so. The world around him tilted on a strange axis, and he thought perhaps it must be spinning. Which was absurd. But it was either that or _he_ was spinning, and Byakuya Kuchiki did not spin. Nor did he tilt. His frown deepened.

The sound of laughter, too loud for his ears, reached him from another part of the restaurant. He attempted to divine its source, but his body was remarkably slow to obey his commands. Before he could properly turn his visual field, someone appeared in it.

"You look like you're not having much fun." The voice matched the laughter. Maybe.

The woman—for indeed the speaker was female—sat down across the table from him. She was wearing a cheap-looking kimono. It was brown, with an apron over it. Byakuya decided it was probably what the staff had been wearing.

"Your observation is irrelevant." His voice didn't sound quite right. Byakuya could not discern if this was because of his mouth or his ears.

"Is it?" She tilted her head to the side.

Byakuya wished she wouldn't. He wasn't sure he could handle more tilting at the moment.

"…yes."

Her mouth curled into a sunny smile, and she reached partway down the table. He tried to track the motion, but failed. She handed him what appeared to be an untouched glass of water. The ice had all long since melted; condensation slicked her fingers, and left a ring on the table where she set it down.

"Trust me when I say you'll want to drink that."

"I don't." He didn't want to drink anything else. He was never doing anything Kyōraku told him ever again. This was beneath his… beneath something. Beneath _him_.

She sighed, and rolled her eyes. "Of course not. Silly me."

Both of them fell silent. He couldn't go anywhere for the moment, as his attempt to stand had amply proven. She simply seemed disinclined, and spent her time studying him.

 _That,_ he was quite accustomed to; he ignored her.

"So, what's got you down?"

The question was quite apropos of nothing. He was confident he gave no sign of being 'down,' in any sense of the term.

"I am not."

"That's bullshit."

The word startled him; he was unused to hearing such vulgarity, particularly from women. Byakuya's eyes moved back to her. She still smiled, which was even odder.

"No one looks that solemn at his own party unless something's going on." She crossed her arms, straightening in her seat. "Come on. You can tell me. You'll most likely have forgotten all of this by tomorrow morning anyway, and it's not like you'll ever come back here."

Byakuya fixed her with a cool stare. "What leads you to such a conclusion?"

"You've thoroughly embarrassed yourself here by being drunk in public. The fewer times you're reminded of this night, the better."

"I am not drunk."

She snorted. "Whatever you say." The waitress leaned forward, placing her elbow on the table and resting her chin in her hand.

For some reason, she hadn't stopped smiling. Perhaps it was the same reason she had not left.

Without his own consent, Byakuya found himself speaking. "I was just promoted to captain," he said.

Condensation dripped down the outside of the glass of water. The droplets of moisture were reluctant to let go of the vessel, clinging until the last possible moment, when gravity pulled them away.

"And…?"

He felt a furrow form in his brow. "I do not believe I am ready to assume the position."

"Hm." Her kimono rustled—she'd straightened a bit. "Your friends didn't seem to have any reservations."

"They are not my friends." The glass wavered in his vision; he was no longer completely certain she'd only given him one.

"That's a shame. They seemed like fun."

There was some undertone to her voice, he thought, but he could not place it. It didn't really matter anyway. Another drop of water, grown too large to hold its place, slid downwards.

"Why don't you think you're ready to be a captain?"

Were there two glasses, or just one?

"…my father died in service to the Gotei 13. I am his replacement. If he were alive, I would not have assumed this duty for another hundred years, at least."

But his grandfather was retiring. There were no other heirs. This, like so many other things, was his duty. His burden to bear. He wondered if anyone else had ever felt stifled by it, or if they were all simply more prepared than he was. It seemed unlikely that they were, but Byakuya could not be sure. Everyone expected _him_ to be.

"Do you want to be a captain?"

He forced his eyes up. She wasn't smiling anymore.

"What?"

"I asked if you wanted to do it."

"That is irrelevant."

She laughed, an inelegant sound that reminded him more of a barking dog than anything else. It grated.

"Irrelevant? Good grief. What the hell do they teach you in that big fancy Seireitei, anyway?" She shook her head, more to herself than him. "'Irrelevant,' he says. Unbelievable."

Byakuya frowned openly at her. He should have expected such an attitude from someone like her. "This is a matter of lineage and duty," he said, flattening his tone as much as his slight slur would allow. "I do not anticipate that you would understand, but you should at least respect it."

This time, when she cracked a smile, he could see the bitterness seeping into the edges. He wondered where it had come from.

"Respect, huh? Yeah… maybe." She sighed. "Wait here and drink your water, _taichō-sama_." The title curled off her tongue with obvious disdain.

Byakuya obeyed, but only because his mouth was suddenly very dry. When the water was gone, he set the glass back down, lining it up with the existing moisture ring on the table.

She returned not two minutes afterwards, a small canister in one hand. "Tea," she explained when his eyes fell to it. "You should make it in the morning, after you wake up. Or have someone else make it for you, I guess." She eyed him thoughtfully. "I think you're probably fine to go now. Just… you know how to get back home, don't you?"

He didn't dignify that with a response. He was not a _child_.

The woman sighed again. "I figured. Okay, here." She held the canister out to him.

Byakuya accepted it dubiously, tucking it up into a sleeve of his shihakushō. This time, his attempt to stand yielded greater success, and after a short moment to steady his balance, he discovered he could walk without much more than mild dizziness.

He left without looking back.

* * *

"So… you didn't get her name or anything?" Rukia picked her tea back up.

It was still warm, but tolerably so, now. The first sip scalded her tongue a little; the second was right at the edge of palatable.

She found it difficult to imagine her brother intoxicated. Surely she had never known him to drink to excess. Then again, this had been more than fifty years ago. From the sounds of it, things were mostly Kyōraku-taichō's fault anyway. That much, she could _easily_ believe.

"I did not," Byakuya replied.

"Then… you went back to the restaurant and saw her again?" Rukia shifted, trying to settle more comfortably into seiza. Her hair was irritating the back of her neck, but she didn't feel comfortable adjusting it. Something about being under her brother's direct scrutiny made it feel like she was already far too undignified; that would only make it worse.

With a barely-perceptible motion, he shook his head. "I did not go back. She told me later that she had been dismissed from her employment there."

"Why?"

"She was apparently in the habit of removing leftover food from the establishment after-hours and distributing it to those she judged to be in need of it."

That surprised her. Theft was… not looked upon well in Soul Society, to say the least. Hisana could have lost much more than her job for something like that.

"So… how did you meet again, then?"

Rukia could have sworn she saw a tiny flicker of amusement on Byakuya's face, but it was gone before she could say for sure.

* * *

The kenseikan felt heavy on his head. Byakuya was tempted to pull it out, since the ceremony was long over anyway, but that seemed inappropriate. He should wait until he returned to his rooms.

He still didn't much favor the idea of it—living in the main chambers of the mansion. They had always belonged to his grandfather, for as long as Byakuya had been alive. Longer, in truth. Since Ginrei was still very much part of the household, it seemed… _wrong_. To assume his titles, to claim even his physical space. But it was his grandfather who had insisted.

In any case, Byakuya disliked his chances of being able to sleep that night, so he instead elected to wander the halls—a ghost in his own home. The servants were long since abed, the guards were posted elsewhere, and what scarce family he had left to him slept as well.

He wasn't likely to encounter a soul. At just this precise moment, he preferred it so.

So naturally, it was then that he heard a noise. It wasn't much, barely a whisper of sound; at any other time, he might have ignored it. But he _knew_ there was no logical reason for anyone to be in this part of the house at this time of night. Pausing in his trajectory, Byakuya stilled his feet on the floor and listened.

He detected no reiatsu.

He was beginning to think he'd imagined the sound when there was another, this one with the distinct hissing edge of a breath expelled between teeth. Byakuya's eyes narrowed. There was a door on his left, one that led into an unoccupied guest bedroom.

Laying one hand on Senbonzakura's tsuka, he placed the other on the door, wrapping his fingers around the edge of the divot in the wood that allowed it to be pulled aside. Lifting up a bit first, he slid the door back with no sound, peering into the room.

Outlined against the moonlight filtering in was a figure. Apparently, someone was attempting to leave his house through his window. Stepping into _shunpō_ , he was behind them in an instant, his hand on the collar of the figure's haori and Senbonzakura's blade pressed to the skin of their neck.

They—she—froze. Unwisely, she turned back over her shoulder to look at him. He adjusted his grip automatically, moving his zanpakutō so that it would not cut.

Her visage was familiar. He believed he'd seen her somewhere before, but she wasn't one of the servants—he knew their faces.

"You've got to be fucking kidding me," she muttered.

The distasteful baseness of her language jogged his memory, and Byakuya frowned, pulling her back into the room by the collar and using his elbow to shut the open window. He let go of her, but not before nudging her shoulder hard enough to force her to turn around and face him. He pointed Senbonzakura at the floor. He wouldn't need to actually reach her with the blade to halt her, if it came to that.

"Explain yourself." He used the same level tone he used for everything else.

"Uh… I think it's pretty obvious what I'm doing here."

He saw a glint at her wrist; it would appear she'd very nearly succeeded in burglarizing his estate. For a scintilla of time, he was more impressed by that than he was offended. It was not the common thief who could make it past the manor's guards without detection. The feeling faded quickly, however.

Byakuya narrowed his eyes. "I could kill you for this."

The Soul Society's law against murder was precious little protection against a noble house.

Her upper lip pulled back slightly; her expression was almost a snarl. "You could," she replied, tone sharp. "It would be petty, spiteful, and arrogant of you, but you could."

Byakuya considered that. It would be petty—she was correct about that. He was less sure on the other two counts. He did not believe he felt spite for this woman. He was displeased that she had caught him in a compromising position last time they met, and uncomfortable with the amount of information he had revealed to her—but none of that was her fault. She had only asked him questions and given him tea.

Come to think of it… he hadn't actually paid his bill.

"Why are you attempting to steal from me?"

She frowned. He did not believe her cheeks had always looked that hollow, and he could not recall the bruise-colored circles under her eyes being present before, either.

"…I didn't know it was _you_ ," she mumbled. "It's nothing personal."

He tilted his head—an invitation for clarification.

She sighed heavily, her shoulders sagging. "Because I'm dying," she replied. The tone of her voice might have matched his for flatness.

"I do not follow."

She raised a dark eyebrow. " _Medicine_ , genius. It's keeping me alive. Couple little things from a house this expensive, and I might live another year. And I really, really want to live." She paused, then shrugged. "Plus I like getting one over on you snob types. You spend so much time checking for reiatsu that you never see people like me who don't have any."

He blinked. "You were gainfully employed previously. Was that insufficient?"

"Are you fucking kidding me? You live in a house like this, and you want to talk about _enough_?" She threw her arms wide, to encompass the guest bedroom. "This room is bigger than the _house_ I live in, and I share it with two other people. Which is damn luxurious compared to some."

He did not reply. She still had not answered his question.

"Oh for— _no_ , okay? It wasn't enough. Not even close."

Byakuya considered that for a moment. Sliding Senbonzakura back into his sheath, he studied her.

One of the things his grandfather had taught him was to look, where possible, for the arrangement whereby all parties were best served. The principle was meant for the context of negotiation with the council or the branch and vassal houses, but Byakuya saw no reason he could not also apply it here.

"How much does your medicine cost you?"

She made a face at him that involved wrinkling her nose, but she answered. The figure was smaller than he'd expected. Was her previous salary really inadequate for such a thing?

"Return what you stole. I will pay you that much to work for me."

Her jaw dropped. "Wait, _what_?"

Byakuya held her eyes steadily. "I do not repeat myself."

Her fists clenched at her side. "Okay, fine. Then _why_?"

"You passed by my guards undetected. If your skill is enough for such a task as that, then I would like to employ you as my messenger. On occasion, I have need for discretion in my communication." As she had rightfully pointed out, a person like her, with no reiatsu to speak of, had a considerable advantage in remaining undetected. She also clearly knew how to stay out of the range of visual detection—and aside from her mistake in letting her guard down once she was almost out the window, she was quiet as well.

Her mouth shut with a click, and she pursed her lips thoughtfully.

"I don't work in the mornings," she told him. "I have other places to be then. But I'll carry your messages in the afternoons, if you want."

She was scarcely in a position to be making demands of him, but they were not an imposition.

"Very well."

She nodded, and silence descended for a moment.

"Hisana."

His left brow ascended a few centimeters.

"My name. It's Hisana. In case you needed to use it. What's yours?"

He blinked. He forgot that sometimes people actually didn't know.

"Byakuya Kuchiki."

* * *

"So… Hisana was already sick before you were married?"

Byakuya inclined his head, taking a sip from his tea before he set the cup down. It wasn't until he'd started pouring the second one that Rukia remembered she probably should have done that. He didn't comment on it though—instead, he gestured for her to put hers down as well. When she did, he refilled it to the top. A fresh coil of steam curled up from the surface.

"For a while, the medicine she purchased slowed the progression of her disease." Byakuya sat back again, taking his cup with him and wrapping both hands around it. "I discovered some time later that she was only taking half the right dose, however."

"Why would she do something like that?"

He shook his head. "I was never certain. There were certain things she simply refused to explain. I had, even then, the sense that something… unsettled her, in a sustained fashion. I did not understand at the time that it was guilt."

Rukia suddenly understood. "You mean… about me?"

"Yes."

Well… at least he didn't mince the words. Rukia pulled in a deep breath. "So… what then? You fell in love with your messenger?"

It was kind of an awkward question to be asking her brother, but he seemed more open right now than she'd ever seen him, almost like talking about this was… pleasant, for him? That was the wrong word, but she didn't know what the right one was.

Byakuya shook his head. "Not precisely, no." He paused a moment, looking down into his teacup like there was an answer in it. "Hisana was… brash. Overconfident. Irreverent. Often self-centered. And the only person I ever felt like myself around. I suppose that to the outside world, it looked as though she were simply my servant, but I do not believe that was ever the case."

He raised the teacup to his mouth and took a sip. Rukia thought that maybe he swallowed a little too thickly for just that, though.

"She was far too easy to confide in. And I seldom noticed how little she confided in return."

* * *

It had become something of a habit of his, to be up much later than the rest of the household. He supposed his continued good function meant he simply didn't require a full night of sleep.

Hisana, of course, stayed up with him, and most nights, they sat on the engawa, he on a cushion next to the table, and she further to the front, always dangling some body part off the lip of the porch into the gardens. That night she lay on her back, parallel to the grain of the wood. Her outside arm toyed with the petals of a flower too close to the edge for him to see.

He frowned at the blank piece of paper on the table, but nothing new came to mind.

So instead, he spoke to her. "Do you ever sleep?"

She huffed, the beginning of a laugh that would never be. Her laughter was not so loud these days. It was a sign of her sickness—though Byakuya would never admit it, he would welcome the uproarious sound it had been before as a herald of her better health.

"I hate sleeping," she replied. "I always wake up feeling like I've missed too much."

He knew she left the mansion whenever she had nothing to do for him.

"Where do you go, instead of sleeping?"

"I wonder…" she murmured, reaching down and snapping the stem of the flower. It made a crisp sound; he heard several drops of water from the day's rain hit the leaves below.

When she pulled her hand up to her chest, Byakuya observed that she held a spider lily. The red color had faded considerably in the lack of light, until it was the dull hue of old blood.

"How are things at the division?" she asked.

His frown etched itself a bit deeper. "I have found myself the subject of a challenge," he replied, sliding his eyes back to the paper.

"A challenge?"

He pretended not to notice how much effort it took her to push herself into an upright position. Some days were better than others, but she rebuffed any attempt to help her—with physical force if she felt it necessary.

Byakuya nodded. "One of the other captains believes he would create a better divisional mascot than I would." Ichimaru was a strange one, but something about him made refusing even a simple challenge unacceptable. It was probably the semi-permanent sly smile on his face.

Hisana snorted. "A mascot? Is this what you big important captains do with your time?"

He blinked. "Not usually. But he implied my skill in the arts was inferior to his. It would be prudent to correct the misapprehension, but I cannot seem to think of an appropriate design."

She smiled and shook her head, shuffling over to the other side of the table. "Give it here, then."

Without _really_ asking for permission, Hisana snatched the paper and brush from his side of the table and dragged them over to her own. She dipped the brush in the inkwell near the middle, then bent over the paper. The tip of her tongue stuck out of one side of her mouth; apparently, she was quite intent on her task.

Byakuya left her to it—she was a wilful person, and he generally found it preferable to avoid argument when she was this focused on something.

"There; done!" She grinned at him, perhaps the largest smile she'd given him since the night they met.

He glanced down at the paper she slid over to him, cocking his head a few degrees to the left.

The mascot she'd drawn appeared to be a mostly-amorphous blot with a face on it, though he could pick out three-fingered arms and a pair of legs. Its expression was, he thought, quite reminiscent of some of Hisana's own. Determined, but tinged with wry humor. She'd written a name at the bottom of the page.

"…You think the best representation of my division is the 'Wakame Taishi'?" he asked flatly. "Also, you are an atrocious artist."

"Hey," she protested. "You shut your mouth, Byakuya-sama."

He'd learned a long time ago to take the honorific with a grain of salt.

"And for your information, he _is_ the best representation of your division, and you. Think about it: seaweed is good, and healthy, but it's kind of sour, and overall pretty bland by itself."

Byakuya honestly wasn't sure whether or not he should be offended. "I do not believe anyone has ever called me bland before," he observed.

"Then no one's ever told you the truth before, because you kind of are."

He hadn't known until just then what it was like to see laughter in someone's eyes. The idiom had seemed wildly inaccurate to him, in truth. But now, looking at Hisana, it clicked somehow, and it occurred to him that the figure of speech had been accurate all along—he had simply never known someone to whom it could be applied.

Any offense he might have taken faded like it had never been present at all.

"What do you mean, when you say that no one has told me the truth?"

She lowered the brush onto the table, taking care not to stain the wood with ink. "Pretty much what I said."

He gave her a blank look.

Hisana sighed. "People are afraid of you, Byakuya-sama. You're a Kuchiki." She waved her hands in a large, encompassing motion. "You own this huge mansion, and that damn scarf that's worth ten more. You don't express your feelings to anyone but your messenger—and you're kind of bad at it even in my case. So you come off like… a cold asshole with no feelings, basically. That works for you, with all the crap you have to deal with, but it can also make you damn scary, especially to us little peons."

His brows furrowed. "You are not afraid of me." Byakuya knew this without a doubt.

It was not a matter of physical prowess. Hisana had no reiryoku, no combat training. Destroying her would not be a difficulty for him, in the objective sense. He knew it, and he knew she knew it as well. But she showed no fear—she never had.

"Scared? Of you? Of course not." Her smile returned. "You don't show _me_ the scary face. Not when you were drunk at my table and not now."

His lips pursed. "I wonder," he murmured, "if that will one day change."

Hisana hummed, slouching a little further and leaning back on her hands. There really wasn't an ounce of elegance or grace to her at all.

"Maybe," she conceded. "But even if I'm afraid, I promise to keep telling you when I think you're being boring, or stupid, or whatever." Her shoulders lifted, then collapsed back down.

Byakuya contemplated that thought for a moment, then inclined his head.

"See that you do."

* * *

"Wakame Taishi was Hisana's idea?" Rukia was familiar with the character—she'd always thought it kind of a weird side of her brother. It made a little more sense now.

He arched a brow, and she thought he _almost_ sniffed.

"Of course. Do you truly believe I would be so poor at the arts?" There was a subtle hint of some feeling at the edge of his voice.

She couldn't identify it. It might have been affront, from someone else. Or even _petulance_. But this was Byakuya. If he was even capable of such a thing, he kept it well to himself.

"Okay," Rukia said, feeling a bit bold. "You draw something then. Here."

She pulled a small ring notebook from her obi—a relic from her time in the living world a year ago. Flipping through several pages of her own art and miscellaneous notes, she paused a moment, tilting her head.

"Huh."

Someone had cut out her dress design and carefully glued it to one of her notebook pages, wedged in between a few of her own mascot designs and some sketches she'd done of the residents of Urahara shop. The neat, thin handwriting on the side of the page notated her dimensions.

"Something interesting?"

She smiled slightly, shaking her head. "It's nothing."

Flipping a few more pages, Rukia found an empty one and handed the notebook over to Byakuya, who was holding his pen in one hand.

"Nii-sama?"

"Yes?"

She hesitated. "Do you like it?" Rukia nodded at the writing instrument in his hand.

He looked faintly confused, following her eyes down to it. "I use it, do I not?"

Her smile grew. "Yeah. I guess it was a silly question."

Byakuya regarded her with narrowed eyes for another few seconds, then turned his attention downwards, pressing pen to paper. The nib made little scratching noises on the surface, just a little different than the soft rasp of brush-strokes.

A suspicion grew in Rukia as she watched him form the lines, one that bore itself out when he sat back, stowing his pen in his shihakushō. She flattened the line of her mouth.

"It looks exactly the same as the regular Wakame Taishi."

"It does not."

There was something odd about Byakuya's voice. Rukia raised her eyes, ready to argue—and then her lips parted in surprise.

He was smiling.

It wasn't overt. If she hadn't been so used to seeing no expression on his face at all, she might not have even counted it as a smile. But for him, that tiny little quirk to one side of the mouth _definitely_ qualified. It made his whole countenance softer, somehow, and she wondered if this was the version of Byakuya that her sister had seen.

Rukia had always been a little afraid of him.

But just then… he didn't seem frightening at all.

* * *

 _Term Dictionary:_

 _Wakame Taishi_ – ワカメ大使 – "Seaweed Ambassador." Mostly shows up in omake segments. Byakuya is weirdly fond of it, and sometimes makes snacks and stuff with the shape. I appropriated it for use here. All three of the Kuchikis are atrocious artists.

* * *

So, as promised, this begins a series of shorter fics and one-shots in the Chaos Theory AU. This is a two-chapter fic, and a second part will be posted soon. I wanted it to give snapshots of important moments in Byakuya and Hisana's relationship (which I envision _very_ differently from most people, I expect), as well as lay some groundwork for development for Byakuya and Rukia as siblings.

I realize my take on Hisana might be atypical, but I think of it this way—we only see basically two moments of her in canon: one where she abandons Rukia, and then another when she's dying. There's a _lot_ of room in between those two things for her to have developed any number of ways. In an effort to minimize the trend of refrigerator-women in the Bleachverse, I'm trying to give her a personality and motivations and agency in her own life, while still keeping to the canon event of her death.

It _should_ all successfully come around to that canon scene in the end, but maybe not in the obvious way.


	2. Chapter Two: Life in Perfect Whole

_Disclaimer_ : While this theoretically _could_ be canon, it isn't.

* * *

 _Adhesion_

A Bleach Fanfic

Chapter Two: Life in Perfect Whole

* * *

The Tuesday after Byakuya had begun his telling of Hisana's story, Rukia found herself leaving the office slightly early to be on time. It wasn't like she'd ben missed too badly—she was an unseated officer, and she'd done all of her paperwork already. No one tried to stop her on the way out, either.

So she made it to the mansion ahead of schedule, only to find that Byakuya was already there. He sat out on the engawa this time, facing in towards the garden. Rukia slid open the glass-paned door and joined him. She had a small argument with herself before settling into a more comfortable cross-legged position instead of seiza. He made no comment about it.

His gardens were really exceptionally well-done. Rukia thought she'd seen the gardener about, on occasion, but she'd never felt brave enough to ask about any of the flowers. Too much in this place still seemed so far away from her.

The tea was already present. Today, there were also cookies. Rukia took one look at them and smiled too widely—they were shaped like the Wakame Taichi. She wondered if maybe Byakuya didn't have a sense of humor in there after all. Picking one up, she bit into it, chewing thoughtfully. It was much more gingery than sweet; she should have expected that. The taste wasn't _bad_ , though. Just unusual.

The silence—in contrast to yesterday's—was comfortable, or something close to it. Rukia thought about how Hisana had once sat exactly where she was sitting now. More than once, according to Byakuya. Her sister seemed like such a fearless person; Rukia could not help but feel the opposite of that most of the time. She wondered, for a moment, how her life might have turned out differently if they'd stayed together, but the thought didn't bring her any bitterness.

"So… when _did_ you fall in love with her?" she asked at last, picking up another cookie.

Byakuya turned his head to observe her from the corner of an eye. Rukia hoped there weren't any crumbs on her shihakushō. She already felt like she was pushing some kind of limit, being as informal as she was.

"I did not. Not in the sense that you intend with the question."

"Wait… what?" She raised a hand to cover her mouth, which was admittedly not entirely empty of food.

"I did not fall in love with Hisana. And she could not fall in love with me."

"But… but you married her! Against the rules and everything." Rukia swallowed too much at once, wincing when it went down.

Byakuya lowered his head fractionally. "Yes."

"I don't understand." She cleared her throat and picked up her teacup, sipping carefully at it in an attempt to wash down the remnants of the cookie. The heat of it made for slow going.

"Then I will tell the rest of the story, and perhaps you will."

* * *

Three years, she had been at his side. Byakuya could not name the moment at which she had transformed from servant to friend. He wasn't even sure 'friend' was the right word. They seemed like the wrong sorts of people to have friends, both of them. What they had instead was… understanding.

She understood that sometimes, he had a need to be Byakuya, instead of Kuchiki-sama or Kuchiki-taichō—and she allowed him to do that without comment.

He understood that there were things she would not talk about. Most of the time, he didn't ask her about them.

Byakuya wondered if she knew that sometimes, he honestly believed that she was all he had, in some sense he could not name. It was an absurd notion—he had everything he could ever need or desire. He had family, and colleagues. Subordinates who relied upon him. Resources enough to want for nothing. Authority enough to impose his will as he saw fit; though he exercised that capacity less often than most assumed.

By some standards, he had everything. He recognized that.

But by others, he had only Hisana.

He supposed she knew—she seemed to have an innate sense for things like that. It was unfathomable to him, but like many other things, he elected not to question it.

"How'd that meeting go with the old men?" She didn't call them the elders, or the council.

"It was acceptable."

"Not if you're making that face, it wasn't." She looked out over the gardens, feet dangling over the edge of the engawa.

"You cannot see my face."

She turned to look at him over her shoulder, propping her chin on it. "Now I can, and my point stands. Something's eating you."

The lines of her face were far too sharp. Years ago, her body had been hale and whole, capable of climbing and running and moving about unseen. She was a pale shadow of that now.

He'd put her in charge of his other messengers. She carried none by herself anymore.

But still, she left every morning like clockwork. And still, he knew not where she went.

It felt wrong, sometimes, to further burden her with his own troubles. But she insisted upon it, and he did not have it in him to refuse her.

"The council have informed me that I must marry."

She scowled openly, wearing with ease the emotions that he could not. "That's stupid."

He didn't think so. Their position was very logical. The Kuchiki family had to stand above any individual member of it. As such, it was necessary for him to ensure its unbroken line with an heir. That was a process for which a wife was necessary. Therefore… he must take a wife.

"Aren't you busy enough with your division and all the other stuff you have to do for your family?"

"I would… prefer to devote my time to the Sixth, yes." His vice-captain may well be retiring soon, and there were few officers suitable to replace him. But even if that were not the case, the division demanded much of his attention. He had little of it to spare. Certainly not enough to maintain the kind of time at home that a noble wife would duly expect. It was the difference between houses with a history of military service and those without. The difference between _people_ who served and those who did not.

"Like I said, stupid."

He released a heavy exhale from his nose. He didn't especially want to talk about it. Byakuya tried one of Hisana's own favored tactics, and turned the question around. "What of you? Have you no intention of marriage or family?"

The question seemed to surprise her. She stared at him blankly for several seconds. Then she laughed, doubling over and holding her sides with the force of it, and it was almost as obnoxious as the first time. He felt himself smile.

"Me? Hell no. I'm not interested in that kind of thing at all."

His smile faded, and he tilted his head. "'That kind of thing'?" he echoed, borrowing her phrasing intentionally.

She shrugged. "Romance. Marriage. Sex. Children. I'm not interested."

He attempted to parse the statement. It was quite direct, as were most of the things Hisana said. But he wondered if he hadn't misunderstood nonetheless. "You aren't interested because you have never encountered someone of the right sort, or…?"

She half-smiled, sighing slightly. "No, Byakuya-sama. I'm not interested in any of it, period. Not in principle, not in reality."

He supposed his expression must have not conveyed sufficient understanding, because she elaborated.

"Love wears a thousand faces. Everyone else in the world seems to be obsessed with the same one or two of them. Me? I'm much more interested in the other nine-hundred-some. I don't care for romance, and I have no desire for anything related to it. That's all."

It wasn't easy to imagine. Byakuya held out no hope that he would experience such things in his lifetime; nobility were not generally permitted to do things like marry for love. But the knowledge that he would never attain or feel such emotion did not halt his natural inclinations towards it. On the contrary—he worked very assiduously to quash them in himself. He supposed she simply lacked those inclinations.

"Your authenticity is admirable," he said at last.

He'd always thought so, in a way. What would have been anathema to him—considering his own desires first, knowing exactly what he wanted and setting his sights on attaining it, living _that_ truly to himself alone—was simply her natural state of being. He could not be like that. Most of the time, he didn't want to. But at times like this…

"You could be a little more authentic yourself, you know," she replied, almost as if reading his thoughts.

"How so?"

She knew he would do what duty demanded. He could not imagine any alternative, and he didn't think she would suggest simple disobedience. Byakuya did not have that option, and he believed Hisana understood.

"Marry _me_ , stupid."

His face contorted in shock, he was sure of it. The grin spreading across _hers_ only confirmed it.

"You just said—I'm not—" He found he had no idea where to even begin.

Her grin stretched wider, gaining an almost jagged edge against the sharpness of her cheekbones and chin. "You're not a very good listener, are you?"

He still had no idea what to say.

She sighed heavily. "I just told you. Love wears many faces. I don't love you _that_ way any more than you love me." Hisana paused, and her expression became unusually serious. "But… I _do_ love you. As much as I've ever loved anyone."

"But—"

"Think about it for a second. If I married you, you'd be able to put the resources of the Kuchiki family behind me. You could have an excuse to call those professional healer people you know." She arched a brow. "I _know_ you've been wanting to do that for a while, but going through all the trouble for a servant isn't _done_ , is it? Your family would have a fit."

That much was quite true.

"And if you married me, you'd get your family off your back, and I wouldn't give a damn how many late nights you worked at the division. It's the solution to both of our problems." She leaned back where she sat, making sure she had his eyes.

It didn't solve the heir issue, and he was not going to ask that of her. But… he was by any standard in Soul Society a very young man. He could figure something out, surely.

"So marry me for love, Byakuya-sama. Let other people misunderstand if they will. _We_ ' _ll_ understand, and that's the important thing."

* * *

"I can't believe she suggested that." Rukia shook her head, utterly astonished. But even more than that… "I can't believe you _agreed_."

Byakuya lowered his teacup, resting it on the palm of one hand, the other wrapped comfortably around it. "Her logic was sound," he replied simply.

"But… wasn't the family against it?"

He dipped his chin. "Very much so. But I told them I would marry her with or without their approval, and in the end, avoiding the scandal was more important to them than the rule against marriage to commoners."

Rukia felt herself begin to smile. "That's… that was pretty sly of you, nii-sama."

"On the contrary; I feel I was quite straightforward in the matter. I loved Hisana, and she loved me. Others marry for much less quite frequently."

Rukia couldn't disagree with that, really. "But still… it wasn't that kind of love."

He shook his head. "No. But it was genuine. More than I had hoped for, prior to meeting her."

She supposed, from his perspective, it must have been. He could have married a stranger, who may or may not have been accepting of his devotion to his division and the Gotei 13. Or he could marry a friend, someone he cared deeply for—who he'd be able to help in doing so. And who didn't mind his priorities. Strange as it was, the choice made sense to her.

"But… I mean, the way you've spoken of her… Hisana wouldn't have made a very good Lady."

"She wasn't." He paused, then amended. "The servants cared for her a great deal, and she for them. But the council disapproved, and that never changed. Fortunately, she was never the sort of person to let that bother her." Byakuya broke a cookie in half and bit into it.

"But if you married her in part to cure her…"

He swallowed; his lips thinned. "She was never one to let the full extent of her weakness show. She hid it from me, and because she asked, even Unohana-taichō did not inform me of just how dire it had grown. I suspect that by the time she suggested the marriage, she was already beyond saving." His eyes fell to his hands. Byakuya turned the teacup around in his hand several times. The words were slower, now, with less of his customary precise diction.

"I think, perhaps, in bringing that up at all, she only… wished to give me a reason to agree. She was fond of saying that our love was an exchange; my resources for her protection from an unwanted betrothal. If I had known I really had nothing to offer her…"

"You might not have gone along with it."

"Yes."

* * *

She was back earlier than usual today. Byakuya could hear the slow treads of her footsteps along the engawa outside—she preferred to enter the manor through one of the side doors, the one closest to her rooms. Even now, few knew that she left the mansion; none knew where she went.

Byakuya stood, moving to the door of his study and sliding it open.

He'd only meant to ask her if she needed anything, perhaps to comment on her unusual return time. But the moment he laid eyes on her, he knew that something was wrong.

"Hisana." He moved to her side immediately.

She was leaning against the wall, one hand braced there to support some of her weight. It trembled—the delicate bones of her wrist had only a paper-thin layer of skin over them. It was uncomfortable for him to look at, even. He could not imagine how uncomfortable it was to endure.

"Byakuya… sama." She turned her face up, a phantom smile flitting over her features for just a moment. Then her knees buckled, and she pitched forward.

It was not effort at all to catch her. In fact, he feared only what would happen if he was _too_ strong in his handling of her. She was rail-thin, wispy in ways she had once been anything but—and so terribly, terribly fragile. He feared even the gentlest touch would break her.

"I'm… fine," she muttered into his shoulder, bracing her hands on his arms and trying to take back her own weight.

"Hisana," he croaked. "Please. Let me help you."

She was going to die. They both knew it, but in all the time he'd intellectually acknowledged that it would happen, he had never _felt_ it so keenly as this. Even at her weakest, her most vulnerable, she had always held herself up. In every sense of the phrase.

He wished dearly now that she would sacrifice just a little bit of that independence to let him support her.

But instead she pushed off him, reestablishing the distance that always lingered between them, filled up by all her secrets and all her pride. Where she was concerned, he had none left. Her breaths were heavy, laborious, raspy. Even the simple, automatic act of living was difficult for her, now.

"I'm fine," she repeated on an exhale. Carefully, she let go of his sleeves and stepped back.

For a moment, she swayed, and he moved to support her again. She stopped him in his tracks with a look; and, though he knew not how, she righted herself again.

"How… is the division today, Byakuya-sama?"

* * *

"She still wouldn't tell you where she went?"

Byakuya shook his head. "No. I wanted to respect her privacy, and until that day, I had. But… I had her followed the day after. I found out she was making trips to Inuzuri."

Rukia poured herself another cup of tea, and filled his as well when she noticed that it was empty. "Did you confront her about it?"

"Yes." He paused to raise his teacup—his eyes were somewhere else. "She still would not tell me. It was difficult to argue with her, given her condition. But it also made it more difficult for her to hide things. It was then I first came to believe she was motivated by a guilt I could not possibly understand."

"Why wouldn't she _tell_ you, though? By her own reasoning, the family's resources would have helped her search." It was odd to talk about, knowing that she herself was the subject of that quest—and already at Shin'ō at the time, most likely.

Byakuya's eyes met hers. "Because she was proud. Prouder even than I. And she would bend for no one." He lapsed into silence.

Rukia waited him out, sensing that there was more he wanted to say.

"There were many things about Hisana that I never knew." Byakuya's voice was soft in a way she usually did not associate with him. Rather than flat, it seemed to have a hint of sorrow to it, a faint tinge of blue-on-grey. "Some she simply would not say. Some, I did not think to ask."

Byakuya set his tea down. "In her, I found many things I needed. And many more I did not. But I do not know what she found in me. Why she loved me and not another. She hated sleeping because she did not wish to miss things. But she missed a great deal, spending so much of her time with me, and I never asked her what she really gained."

Rukia pursed her lips. "I didn't know her," she said slowly. "But I think she gained plenty."

He tilted his head at her.

"…Perhaps."

"So… how did you find out about me, then?"

* * *

Her hand was cold.

He'd opened the window for the spring warmth and the fresh air, but it did little for her. Hisana's breath was ragged, her complexion drawn and face wan in the extreme. Her illness had only accelerated in the last year, and not even Unohana's best efforts could break its hold. She'd been bedridden for three months.

Byakuya thought that this was what had finally broken her spirit. Without even enough strength to maintain her routine, her trips into the Rukongai, it seemed almost as though she'd just… given herself over to inevitability.

She turned her head to look at him, squeezing his fingers weakly. Her lip quirked. "Don't… show me that face," she murmured.

He lacked the wherewithal to respond.

"You wanted to know… why I went to Inuzuri." Her eyes fell away from his face, and she fixed them out the window.

"Yes," he rasped. Though he wasn't sure it mattered anymore.

Her eyes fell half-lidded, like they were too heavy to hold open. "I have… I had a sister, once. We were both… brought to Inuzuri after we died. She was just… just a baby." She had to pause, pushing and pulling several breaths from her lungs. "I didn't even remember her name, and she wasn't old enough to tell me. I…"

Hisana's whole body shuddered. Byakuya inched closer on his knees, rubbing his thumb along the back of her knuckles.

"I was selfish. Just like always. I… I left her behind. I couldn't… look after her and myself, too… and I wanted…" Another gulp of air. "I wanted so badly… to live." There was a bitter twist to her mouth.

"Eventually I… found a job, and a place to stay, and I… I realized what I'd done. I had to find her."

Suddenly, he could make sense of it. Her stubborn insistence on going to Inuzuri every day. Her equal obstinacy in keeping the task something for herself alone.

"You…" she huffed softly. "You—you're always so conscious of your family. You would… you would have starved or died before you did that." Her eyes closed slowly.

Byakuya went rigid, afraid for a moment that she would not open them again. But then he could see a sliver of blue-violet iris again, and relaxed just slightly.

"Byakuya-sama… please. Find my sister. Then after you find her… please do not tell her that I am her family." She swallowed; the action seemed to pain her. "Without telling her anything… please protect her, no matter what."

"Hisana—" He cut himself off when she started to speak again.

"I abandoned her, so I don't deserve to be her family, but… I hope that she can be yours. Like I was, for just a little while." She smiled thinly.

Byakuya felt something squeezing his chest, like climbing vines choking the life from a tree.

"Even at the very end… I am still asking more of you." She shook her head—several strands of lank hair fell in her face.

Byakuya bushed them away with trembling fingers.

"It looks like… I couldn't return your love after all. I'm sorry." Her eyes closed again. "But I wanted you to know… that these years with you… were like a dream for me. And I want… that dream for her, too." She pulled in a halting lungful of air.

"Thank you… Byakuya-sama."

Her chest fell as the breath left her, and her hand went limp in his.

* * *

It was quiet for a long time. Byakuya seemed to be lost to the memory. Rukia didn't think she should interrupt.

Instead, she turned her eyes down, to her tea. She couldn't imagine what he must have felt like. Even if their relationship wasn't exactly what everyone else thought it was… it was clear enough to her that it had been profound. Hisana had been there for him when no one else had understood how he felt. And… despite his belief to the contrary, Rukia thought that he'd been there for her sister, too.

Maybe… maybe she did understand, a little bit, what that was like. She thought she'd felt that kind of love before. Perhaps Hisana had been right, about that emotion having a thousand different faces. Her sister's love for Byakuya had been the kind that was always truthful, even when that meant being hard or disagreeable.

"Nii-sama," she said, glancing up.

He shifted, and it was like his whole being snapped back into focus.

"I… can't be Hisana. I'm not that much like her, I don't think. But… I can make you the same promise she did. That I'll always tell you the truth. That I won't be afraid just because of who you are." She, unlike Hisana, _had_ been.

But somehow, she felt that she didn't have to be. She could choose not to be. They had the power to change what they were to each other—Hisana certainly had. And Rukia was tired of drinking tea with a stranger on Tuesdays.

Byakuya considered that. "Then… I will promise you something as well." He paused thoughtfully. "For as long as we are family, you need not fight your battles alone. I will strive to become as a brother should be… Rukia."

She nodded. That would be their kind of love. And Hisana would have her wish.

* * *

 _Notes:_

That's a wrap on this one. I'd intended for it to have a snapshot feel, rather than being a whole narrated thing, and I wanted to keep the perspective to the characters who were alive in the framing device, since it wouldn't make sense for Byakuya to be telling Rukia a story from Hisana's perspective.

And yes, Hisana was aro/ace. I don't know how that became my headcanon, but there you have it. I think the whole thing hangs together pretty well with canon; I managed to use the vast majority of the canon lines in Hisana's dialogue during the death scene, plus a few more things to expand on it.

Younger Byakuya was a little more expressive than older Byakuya, which makes sense if you think of stoicism as something you might have to work at.

But anyway. I hope it was enjoyable, and if nothing else, it's a bit of background information and a bit of familial progress for _Chaos Theory_ , so there's that.

The next fic will be Renji-centric. It's called _Triple Point_.

* * *

Reviews appreciated as always.


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